Yesterday I went to zero the rifle, from a rest, no pressure upon the upper at all, not even from a sling. It grouped very well, but very far to the right.
The rear sight has 40 clicks of adjustment, 20 to the left, and 20 to the right. I have the rear sight aperture 12 clicks to the left to zero the windage. Elevation was no problem, almost spot on from the get go.
I do not think that this is due to a canted front sight base, or an improperly milled picatinny rail on the upper receiver.
I took a piece of thread and fed it through the small aperture of the rear sight, and looped it around the front sight post, and pulled it taught. I then took photographs, and oriented them using the photo software with a grid so that the milled slots from the picatinny rails meshed perfectly with the horizontal lines on the grid. The string made a perfect straight line that meshed with the vertical lines on the grid.
The string seemed to stay proportionally in the middle of the barrel on multiple pictures (to attempt to take into account paralax errors), indicating that the line of the sight through the sight picture does indeed go over the middle of the barrel.
I therefore believe that the front sight/gas block and upper receiver are indeed square to each other, but that the rear sight is not manufactured properly. What is your opinion on this matter?
Full size and quality images can be emailed upon request if you want to see the high res photos, but below is what photobucket will let me put up.
(http://i151.photobucket.com/albums/s127/jeep45238/Range%20Time/545%20AR15/Windage%20Error/DSCN0002.jpg)(http://i151.photobucket.com/albums/s127/jeep45238/Range%20Time/545%20AR15/Windage%20Error/DSCN0003.jpg)(http://i151.photobucket.com/albums/s127/jeep45238/Range%20Time/545%20AR15/Windage%20Error/DSCN0004.jpg)(http://i151.photobucket.com/albums/s127/jeep45238/Range%20Time/545%20AR15/Windage%20Error/DSCN0005.jpg)(http://i151.photobucket.com/albums/s127/jeep45238/Range%20Time/545%20AR15/Windage%20Error/DSCN0006.jpg)(http://i151.photobucket.com/albums/s127/jeep45238/Range%20Time/545%20AR15/Windage%20Error/DSCN0007.jpg)
It might be the photograph, but your rear sight doesn't look to be perpendicular to the rail.
Double check that it is attached properly as I bet there is something wrong there or the rear sight is literally bent.
It's mated flush against the rail - and yes, the right side does literally appear bent to me. One of those "I'm pretty sure this is what's going on, but maybe it's just my eyes" things.
Is the front sight slightly canted there. Turn in around and look at it from the front. See if it has a bit of the old AK cant to it.
Sure doesn't look like it. I'm using the milled portion of the rails as a reference and comparing it to the milled portion of the front sight base, sure looks square to me.
That should also eliminate the possibility of the barrel not being normal to the receiver's axis.
Looks like you have one screw putting pressure on the rail and it is up front? Could that be shoving the entire sight right and slightly crooked?
Very curious.
Quote from: techres on October 09, 2010, 07:44:55 PM
Looks like you have one screw putting pressure on the rail and it is up front? Could that be shoving the entire sight right and slightly crooked?
Very curious.
I'm curious as well!
It's one screw/crossbolt holding a Daniel Defense A1.5 rear sight, through the recess of the milling. The sight is tight, and flush at the front where it interfaces with the underside of the rail profile, and at the rear.
Even a cant would have to be pretty excessive to get this kind of windage correction to be necessary.
I've gotta get running and go to work, but feel free to keep tossing ideas and I'll check 'em out when I get home :D
Just by looking at the pictures the rear sight looks kind of funky. If you had the chance I would take the rear sight off and try a different one on it to either eliminate it or find the fault.
Factory assembled upper or home built? I had a very similar situation with a lower quality upper and after we removed the barrel to install a free float tube and reinstalled the barrel to proper torque it no longer had the issue. I do not necessarily believe it was the free float tube that corrected it though.
Good luck.
I don't know what all you have tried so here's what I would do.
If you have a carrying handle or another BUIS of course try that.
remove then reinstall the site. If no change,
Move the front sight post 1-2 clicks. If it is slightly bent, that will show a zero change.
If you track it down to the sight Daniel Defense has awesome Customer Service. Matter of fact, I would send your pics to joe@danieldefense.com just to get dialogue going.
I have seen many sights worse, though. Worse case, I will trade you a Matech flip up for it. O0
Is your front sight pinned? If not, just rotate the front sight block. I have one like this and it is amazing how little movement it takes to make a huge change in point of impact. I made a witness marker with an ultrafine sharpie and all I had to move it was the width of the sharpie line.
Quote from: bedford on October 10, 2010, 08:11:19 PM
Is your front sight pinned? If not, just rotate the front sight block. I have one like this and it is amazing how little movement it takes to make a huge change in point of impact. I made a witness marker with an ultrafine sharpie and all I had to move it was the width of the sharpie line.
Yup, it's pinned. Not going to mess with the gas block/front sight base and gas port relationship on this. It's a 5.45, not a standard caliber for an AR, and I have no clue how much wiggle room there is before the gas port would get blocked. Granted, it did cycle with a 4.3oz buffer and a 10% extra power spring on Wolf 5.45, but still.
Quote from: U.S.Cavalryman on October 09, 2010, 08:39:21 PM
I don't know what all you have tried so here's what I would do.
If you have a carrying handle or another BUIS of course try that.
remove then reinstall the site. If no change,
Move the front sight post 1-2 clicks. If it is slightly bent, that will show a zero change.
If you track it down to the sight Daniel Defense has awesome Customer Service. Matter of fact, I would send your pics to joe@danieldefense.com just to get dialogue going.
I have seen many sights worse, though. Worse case, I will trade you a Matech flip up for it. O0
Thanks for the suggestions.
I'll have to pass on the Matech trade though, thanks - this is going to stay a KISS iron rifle, and I won't want anything with joints on my sights :)
My two cents,, sounds kinda cheesy but you can add a shim to the mount. Picatinny is a bit forgiving.
http://www.brownells.com/.aspx/pid=589/Product/KIT_NO__AC_24_STEEL_SHIM_STOCK (http://www.brownells.com/.aspx/pid=589/Product/KIT_NO__AC_24_STEEL_SHIM_STOCK) cut to fit.
Quote from: NewMOe on October 11, 2010, 10:40:03 AM
My two cents,, sounds kinda cheesy but you can add a shim to the mount. Picatinny is a bit forgiving.
http://www.brownells.com/.aspx/pid=589/Product/KIT_NO__AC_24_STEEL_SHIM_STOCK (http://www.brownells.com/.aspx/pid=589/Product/KIT_NO__AC_24_STEEL_SHIM_STOCK) cut to fit.
I'd need to shim a solid 20 thou, if not more - I'd rather mess with the gas block than a shim (feeler gauges are cheap though :) )
Quote from: jeep45238 on October 11, 2010, 03:44:52 PM
Quote from: NewMOe on October 11, 2010, 10:40:03 AM
My two cents,, sounds kinda cheesy but you can add a shim to the mount. Picatinny is a bit forgiving.
http://www.brownells.com/.aspx/pid=589/Product/KIT_NO__AC_24_STEEL_SHIM_STOCK (http://www.brownells.com/.aspx/pid=589/Product/KIT_NO__AC_24_STEEL_SHIM_STOCK) cut to fit.
I'd need to shim a solid 20 thou, if not more - I'd rather mess with the gas block than a shim (feeler gauges are cheap though :) )
Since your block is pinned you will not be able to move it. If I were you I'd just live with it as it is a short range setup and you probably won't be moving the windage anyway, especially with the A1 knob. I am sure Daniel Defense will swap out the sights with you. If that doesn't fix it, and if it is that important to you, send the upper back to Spikes and I am sure they will fix it.
No matter all the careful calculations, the front sight base needs to be bashed with a plastic hammer from the right. About the width of a sharpee witness line drawn on the barrel and front sight base. The front sight base will rotate with the pins in place. Be sure to put the barrel in a vice.
Also, you don't have to worry about the gas port, It will still flow air at unbelievable angles.
This is highly technical "gunsmith" work. If you don't feel comfortable doing it, just shoot the rifle like it is. I have never felt comfortable charging a customer to fix this "problem". I do it for free.
I have an AR with the exact same problem. So far I've changed out the roll pins on front sights, removed and retorqued the barrel, then swapped upper receiver with my other AR. To date no change. It like the idea of turning the front sight a couple clicks and if that doesn't work trying the hit from the right with the plastic hammer. Otherwise I'm ready to replace the barrel. This is my first AR bought over 20 years ago for a very low price. The barrel is heavy but has absolutely no markings on it. No mfg., no twist, nadda. Someone commented maybe it was used and saw a lot of automatic fire and could have warped. Not sure but could be plausible explanation.
Jeep, I had to try to get that DD, lol.
One more thing to try, I would eith let someone else check the zero, and/or shoot it with non dominate side. The zero should be very close.
Quote from: dean on October 12, 2010, 12:41:53 AM
No matter all the careful calculations, the front sight base needs to be bashed with a plastic hammer from the right. About the width of a sharpee witness line drawn on the barrel and front sight base. The front sight base will rotate with the pins in place. Be sure to put the barrel in a vice.
Also, you don't have to worry about the gas port, It will still flow air at unbelievable angles.
This is highly technical "gunsmith" work. If you don't feel comfortable doing it, just shoot the rifle like it is. I have never felt comfortable charging a customer to fix this "problem". I do it for free.
+1. This is what you do.
-David
Edgewood, NM
The fix is as they say, & can be done a number of ways.... Green or red locktight used on the barrel and front sight base/gas block and cleaned off the gas system will keep things in place forever under normal use, some shoddy gas blocks are out there along with some seconds in the front sight base that show up for sale from time to time... Pappy
Jeep,
Been building M4's for about 4 months for the navy. A few things I have found out:
When zeroing M4's we find out that most of the time we can go up to 15 clicks before an upper receiver fails, and has to be rebuilt. This leaves enough wiggle room to make adjustments in high winds.
If the front sight base is canted, there's not much you can do about it, except take off the barrel and send it back to manufacturer. We failed one barrel last week because it was canted so badly we couldn't get the rifle to hit a 5'x5' cardboard backer at 25yd. The front sight base usually can't be re-fit - the pins generally go in only one way, and come out one way, and usually can't be reworked. We just fail them and return them.
The MOST COMMON reason for this to be SO FAR over is due to excessive torque or not enough torque of the barrel nut onto the upper receiver. Generally we replace the barrel into another upper, and put the upper with another barrel, and it solves the problem.
I would try what some of the other people here have suggested, and make rear sight changes, try a different carrying handle, etc, before you resort to this (returning the upper). But if I looked at it and the front sight was not canted, and the rear sight was not all kinds of messed up, I would say it was a barrel fit issue. However, I think with 8 more clicks to the left, you'll be okeydokey.
Just my 2c.
West :))
Interesting about hte barrel nut torque - I was just reading up on some of that.
Maybe they didn't torque it three times, who knows. Guess I've got a barrel nut to loosen and re-torque later today :)
I have an AR with this exact same issue - on mine it was too much play between the lug and corresponding slot that controls the clocking of the barrel where it interfaces with the upper receiver. I made some little shim tabs to fill that gap and stop the barrel against rotating CW while torquing the barrel nut - the front sight is still a little too far left but better than it was.
You may have tried re-torquing that nut already, but if not, while it's loose, grab the gas block and see how much rotational play you have between the barrel and upper.